On 2008-07-17, Jon Elson wrote:
Ignoramus30183 wrote:
I wired the VFD to the lathe. Not in the best way yet, but enough to
experiment. Toshiba VF-A3 3.7 kW VFD, similar to what I sold to Pete
C, only bigger and with cracked top cover. (I have more for sale, 2.2
and 3.7 kW)
Here's one very encouraging piece of news (related to what Karl said):
switching of the speed selector lever while the motor is running does
not destroy the drive. It simply trips on a overvoltage error and lets
the lathe coast to stop.
I am very satisfied with this behavior. It is as perfect as it gets.
The drive can easily accelerate the lathe, even at the highest
speed setting, etc.
Right now it trips when I press OFF, no doubt due to too ambitious
braking that is the default setting right now.
What I need to do is:
1) A lot of settings need to be set such as no braking, fixed
frequency (60 Hz), one-two second acceleration, etc etc.
Braking is GOOD, a real safety feature. Even if you have to cobble up a
braking resistor, it is well worth it. I get less than one second stops
on my 15" Sheldon, with a pair of 100 W vitreous enamel resistors wired
up to the braking circuit.
Does your sheldon include a mechanical brake?
Are your 1 second stops, actually happening at high spindle speeds?
My drive already has a braking resistor, IIRC. Some of mine do and
some don't. But even if not. I have some resistors.
2) Wire it properly to turn on with the limit switch operated by lathe
ON/OFF/BRAKE lever
Yes, that would be really nice.
I already did so, it is awesome.
I have the original forward/reverse/stop buttons on my Sheldon
hooked to the VFD, and it is quite nice. I added a jog button, that
is nice for when the gears don't engage.
What is your jog frequency?
Myself, when gears don't engage, I just grab the chuck and rock it a
little.
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